1. Field of the Invention
The present invention relates to a reaction gas cooler, which is primarily used for low-energy plants, for example in ammonia-producing plants. The reaction gas cooler includes a refractory lined gas inlet, a first stage in the form of a tube bundle heat exchanger through which the gas flows, an intermediate chamber, and a second stage in the form of a tube bundle heat exchanger through which the gas flows.
2. Description of the Prior Art
With such low-energy plants, the heat of the reaction gas is to be utilized to the greatest extent possible for producing saturated steam or vapor.
In order to take advantage of the sensible or perceptible heat of the reaction gas in previously existing plants, it was generally necessary to utilize, among other things, a feed-water heater. In low-energy plants, for reasons of overall heat balance, the feed-water heater must be replaced by a second evaporation stage. However, in so doing the following problems arise: For heat-transfer reasons, the length of the heretofore known cooler is limited to approximately 6 m, since only extremely thin tube sheets or plates can be used which, if the cooler has any greater length, would bend due to their elasticity. However, for an optimum gas inlet velocity, in nearly all cases, design computations result in greater overall structural lengths for the cooler. Thus, in order to achieve the theoretical heat transfer surface, the only possibility remaining was to increase the number of tubes. However, this reduces the velocity of the gas, the consequence of which is a poorer .alpha.--value. Thus, it is inefficient to increase the heat transfer surface. Another problem is the by-pass tubes, which are necessary in order to keep the exit temperature constant. For this purpose, cooled gas must be mixed with hot gas, possibly accompanied by continuous readjustment.
An object of the present invention is to provide a reaction gas cooler which, without increasing the overall length, makes it possible to have an optimum gas inlet velocity in each stage, and with which the by-pass tubes for keeping the exit temperature constant can be eliminated.